1. Field of the Invention
The present invention relates to an ink jet recording apparatus for forming an ink image by ejecting ink from a printhead, and a liquid absorbing member for removing ink components from the ink image.
2. Description of the Related Art
Color documents are in wide use in offices recently, and various output devices have been proposed. In particular, the ink jet method, that is miniaturizable and inexpensive, is used in various output devices.
A printhead used in the ink jet method comprises as energy generating portion, an energy converting portion for converting the energy generated by the energy generating portion into an ink ejecting force, an ink ejecting port for which ink drops are ejected by the ink ejecting force, and an ink feeding route communicating with the ink ejecting port for supplying ink drops. Examples of the energy generating portion include a portion using electromechanical converting elements such as a piezoelectric element, and a portion which heats an ink by an electro-thermal converting element having a heat generating resistance element to generate foams, and ejecting ink drops by this generation of foams.
In such ink jet methods, ink is mainly composed of liquid components. Therefore, when ink drops remain on the recording medium after being ejected onto a recording medium, they may be transferred to another recording medium. This phenomenon is more obvious in high speed printing. Further, when the system that uses another treating liquid in addition to ink (namely, a two-pack system) is used in order to achieve higher image quality, the volume of the liquid increases. Thus, as compared with when the treating liquid is not used, a larger amount of liquid is absorbed by the recording medium, and accordingly curling and/or cockling are more likely to occur. When printing on the reverse side is conducted, head rubbing occurs, which causes image quality deterioration.
In particular, when ink jet recording is intended to be applied to the printing field, it is required to be able to be used for printing on an impermeable recording medium such as art paper, which is a coated paper, or resin film. Since such impermeable recording media basically hardly absorb liquid components of ink therein, the problem of image quality deterioration from unfixed colorant in the printed ink image becomes apparent.
Hence, various methods have been proposed to heat or send air in order to quickly dry printed media after the media have received ejected ink. In these methods, however, energy consumption increases, and a large apparatus is needed. On the other hand, there is a method in which an excessive ink liquid remaining on a recording medium is absorbed by paper, however, colorant components in the ink image may be absorbed at the same time, and therefore is not practicable.
In particular, when printing is conducted by using the above-described impermeable recording media, an additional step of removing liquid components other than colorant components in the ink image after printing is required. Further, in order to assure image quality, a proper method is desired so as not to deteriorate the image or press and damage the image.
In order to absorb only liquid components (liquid solvent) of ink, it has been proposed that only excessive liquid (liquid solvent) of ink remaining on the recording medium be absorbed by using a liquid absorber covered with a member having the property of releasing from a coloring agent (colorant) after printing (after ink is ejected on a recording medium) (see, for example, Japanese Patent Application Laid-Open No. 2001-179959).
In this proposal, however, since the liquid absorber is made of a material having the property of eleasing from the coloring agent disposed on a contact side (surface) with the liquid solvent, it also parts from the liquid solvent, and thus cannot sufficiently absorb the liquid solvent. Moreover, since a hydrophobic portion is present on the surface, the ink is rejected, which causes deterioration in image quality.
When liquid volume is increased by using a treating liquid in addition to ink or when high speed printing is conducted, it is desired that ink components be absorbed quickly, however, the above-described method is not sufficient.
Moreover, since this method is designed to absorb ink by pressing a roller having a liquid absorber, the image may be pressed and spreading may occur, and an image of high quality may be spoiled in particular when an impermeable recording medium is used.